The background of the invention will be discussed in two parts:
1. Field of the Invention
This invention relates to roller skates or skateboards or the like, and more particularly to such devices having two wheels.
2. Description of the Prior Art
In roller skates or skateboards, there is a rider supporting member such as a soleplate in the case of a roller skate or a board in the case of a skateboard, which rider supporting member has in depending relation therewith, a pair of trucks, each of the trucks having rotatably coupled thereto a pair of wheels, with the truck being designed and configured for causing the two axles, which are normally parallel to each other, to simultaneously pivot in opposite directions upon shifting of the weight of the rider to thereby cause the wheels to traverse a curved path. Such roller skates or skateboards employing two pairs of wheels have certain functional limitations due to the requirement that each pair of wheels have some structure for supporting the axle therebetween. Furthermore, roller skates of such construction are generally unable to approximate the smooth stroke of an ice skate wherein the blade of the skate effectively defines a line of contact with the surface on which the skate is used, the center of gravity of the foot of the rider normally being applied downwardly through the plane of the blade.
Attempts have been made, in roller skates, to utilize two wheels on each roller skate, with one wheel toward the toe and the other wheel toward the heel of the soleplate, such two wheel roller skates being shown and described, for example, in U.S. Pat. No. 1,558,404 and 3,999,772. The construction of each of these patents has the axle of each wheel in fixed relation in parallel with the other. No steering means are provided.
Two wheel roller skates of the steerable variety are shown and described in U.S. Pat. No. 181,868; 2,204,280; and 2,719,724. In the last of the three above-mentioned patents a connecting shaft with bevel gears on either end interconnects with a bevel gear on each of the wheel supporting members which rotate about a vertical axis with spring means interconnecting the roller or wheel supporting members. In such a construction, the soleplate is either spaced high relative to a supporting surface or the diameter of the wheels must be made correspondingly small to move the soleplate, and consequently the center of gravity of the rider, closer to the surface. In U.S. Pat. No. 181,868 an elaborate set of arms and linkages is employed in a two wheel roller skate construction using glass wheels.
In U.S. Pat. No. 2,204,280, a two wheel roller skate construction is shown in which the wheels are supported within axle forks which are resiliently limited to enable the rollers or wheels to deflect into an oblique position for travelling in a curve.
A skateboard utilizing two wheels is shown and described in U.S. Pat. No. 3,995,873.
In steerable two wheel rider supporting devices, there are two axes of interest relative to each truck or roller assembly, these axes being the wheel supporting axle or axis and the "steering" axis. The wheel supporting axis is normally the axle of the wheel which defines the center of rotation thereof and so long as the wheel is in ground engaging contact, this axis is normally parallel to the ground unless the wheel itself is contoured to enable the wheel to pivot relative to the ground. The "steering" axis, on the other hand, is defined as the axis about which the rotatably supported wheel pivots to enable the wheel axle to pivot relative to the longitudinal center line of the rider supporting member, be it a soleplate in the case of a roller skate or a board of a skateboard. The wheel supporting axis or axle in a two wheel rider supporting device structure extends on a line normally perpendicular to the longitudinal center line of the rider supporting member, the plane of the rider supporting member being normally parallel to the plane through which the wheel axis extends. In a steerable structure, as the weight of the rider shifts the plane of the rider supporting member is angularly disposed relative to the plane of the wheel axles and the individual axles rotate or pivot simultaneously in opposite directions relative to the longitudinal center line of the rider supporting member. This effects "steering" of the rider supporting device and in the above-mentioned U.S. Pat. No. 2,719,724, for example, the steering axis would be a vertical axis of rotation of the wheel or roller supporting member.
In the roller skate and skateboard structures of prior art devices, the steering axis generally lies above the plane of the wheel axles, the steering axis in such prior art devices generally being vertically disposed relative to the rider supporting member or at an angle to the vertical. In such devices, the center of gravity of the total system, that is, the rider supporting device with the rider, is high relative to the supporting surface such as the ground or the like. Furthermore, in many of the prior art devices, the wheel tread width is too narrow resulting in the center of weight of the rider during pivoting of the rider supporting member exerting a force outside the width of the tread. That is, if an imaginary line were drawn perpendicular to the rider supporting member and through the longitudinal center line thereof, ideally to maintain traction, this line should intersect the ground within the width of the tread of the wheel and preferably as close to the center as possible. When this line extends outside the width of the tread of the wheel due to the plane of the rider supporting member being pivoted angularly relative to the ground or supporting surface, an unstable system results with more force being exerted laterally than downwardly.
Accordingly, it is an object of this invention to provide a new and improved rider supporting device such as a roller skate, skateboard or the like.
It is another object of this invention to provide a new and improved two wheel rider supporting device.
It is a further object of this invention to provide a new and improved truck for a rider supporting device wherein the steering axis lies below the plane of the wheel axle.
Other objects, features and advantages of the invention will become apparent from a reading of the specification when taken in conjunction with the drawings in which like reference numerals refer to like elements in the several views.